Rotational alignment mechanism for load cups

ABSTRACT

The present invention generally relates to a substrate transferring system having an alignment mechanism of a surface and to two points. One embodiment of the present invention provides a load cup for transferring a substrate. The load cup comprises a cup having a substrate supporting surface configured to support the substrate thereon, and two alignment pins protruding from the cup outside the substrate supporting surface, wherein the two alignment pins are both positioned at a first distance away from a center of the substrate supporting surface, and the cup is pivotable about a pivoting point positioned at a second distance away from the center.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 60/810,350, entitled “Rotational Alignment Mechanism for New Load Cup”, filed Jun. 2, 2006, which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to an apparatus and a method for transferring a substrate.

2. Description of the Related Art

Sub-micron multi-level metallization is one of the key technologies for the next generation of ultra large-scale integration (ULSI). The multilevel interconnects that lie at the heart of this technology require planarization of interconnect features formed in high aspect ratio apertures, including contacts, vias, trenches and other features.

Planarization is generally performed using Chemical Mechanical Polishing (CMP) and/or Electro-Chemical Mechanical Deposition (ECMP). A planarization method typically requires that a substrate be mounted in a carrier head, with the surface to be polished exposed. The substrate supported by the carrier head is then placed against a rotating polishing pad. The carrier head holding the substrate may also rotate, to provide additional motion between the substrate and the polishing pad surface.

A load cup is generally used for substrate transferring to and from a carrier head. During the substrate transferring process, good concentricity/alignment between the carrier head and the load cup is desired to ensure fast, reliable and safe substrate hand off between the load cup and the carrier head. The alignment mechanism in the state of the art system generally includes sliding a tapered surface of on the load cup to a tapered lip on the carrier head. This alignment mechanism has a few limitations including limited capture range, requiring precise surface control over large area, and uncertain mate condition since the mate is over a tapered surface to a tapered surface.

Therefore, there is a need for an apparatus and method to improve substrate transferring between a load cup and a carrier head.

SUMMARY OF THE INVENTION

The present invention generally relates to a substrate transferring system having an alignment mechanism of a surface and two points.

One embodiment of the present invention provides a load cup for transferring a substrate comprising a cup having a substrate supporting surface configured to support the substrate thereon, and two alignment pins protruding from the cup outside the substrate supporting surface, wherein the two alignment pins are both positioned at a first distance away from a center of the substrate supporting surface, and the cup is pivotable about a pivoting point positioned at a second distance away from the center.

Another embodiment of the present invention relates to a substrate transfer assembly, comprising a load cup comprising a substrate supporting surface having a center, the substrate supporting surface configured to support a substrate thereon, and two alignment pins protruding from the load cup at a first distance away from the center, a shaft extending from the load cup at a second distance away from the center, and a supporting arm pivotably connected to the shaft, and a carrier head having a substrate receiving surface configured to receive a substrate, the carrier head is relatively movable from the load cup.

Yet another embodiment of the present invention relates to a method for aligning a load cup with a carrier head for transferring a substrate comprising providing two alignment pins extending from the load cup, wherein the two alignment pins are configured to align the load cup with the carrier head, providing a pivoting point about which the load cup may rotate, wherein the pivoting point is away from a central axis of the load cup, moving the carrier head and the load cup relatively such that the carrier head is in contact with one of the two alignment pins, pivoting the load cup about the pivoting point such that the carrier head is in contact with both of the two alignment pins.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 illustrates a partial sectional view of a state of the art system for substrate transferring.

FIG. 2 illustrates a partial sectional view of a substrate transferring system in accordance with one embodiment of the present invention.

FIG. 3A illustrates a top view of the substrate transferring system of FIG. 2.

FIG. 3B illustrates a top view of the substrate transferring system of FIG. 2 at a pivoted position.

FIG. 4A and 4B illustrate an exemplary method for aligning a load cup and a carrier head.

FIG. 5 schematically illustrates a capturing range for the substrate transferring system of the present invention.

DETAILED DESCRIPTION

The present invention generally relates to an apparatus and a method for transferring a substrate, particularly relates to substrate transferring between a load cup and a carrier head in a chemical mechanical polishing (CMP) system or electrochemical mechanical polishing (ECMP) system.

FIG. 1 illustrates a partial sectional view of a state of the art polishing system 100. The polishing system 100 includes a polishing station 102, a carrier head 104 and a load cup 110. The polishing station 102 includes a rotatable platen 106 having a polishing material 116 disposed thereon. The carrier head 104 is supported above the polishing station 102 coupled to a base 126 by a transfer mechanism 118. The transfer mechanism 118 is adapted to position the carrier head 104 selectively over the polishing material 116 or over the load cup 110 (shown in dotted lines). The carrier head 104 comprises a housing 140 having an extending lip 142 defining a recess 146. A retaining ring 150 circumscribes the carrier head 104 to facilitate retaining a substrate within the carrier head 104. The load cup 110 generally includes a pedestal assembly 128 configured to support a substrate thereon and a cup 130. The pedestal assembly 128 is supported by a shaft 136 which is coupled to an actuator 133. The cup 130 is supported by a shaft 138 which extends through a hole 134 in the base 126 and is coupled to an actuator 132. When transferring a substrate between the load cup 110 and the carrier head 104, the carrier head 104 is generally rotated to above the load cup 110, as shown in the dotted lines. The pedestal assembly 128 may be raised so that the inner surface of the retaining ring 150 mates with the outer surface of the pedestal assembly 128. The outer surface of the pedestal assembly 128 and the inner surface of the retaining ring 150 may be tapered to ease the mate. However, transferring substrates in this configuration generally has limited capture range, requires precise surface control over large area and uncertain mate condition. Transferring mechanisms of the present invention overcome or improve these limitations.

FIG. 2 illustrates a partial sectional view of a substrate transferring system 200 in accordance with one embodiment of the present invention. The substrate transferring system 200 generally comprises a load cup 201 and a polishing station 230 having a carrier head 231.

The polishing station 230 generally comprises a shaft 235 coupled to a base 236. A swing arm 233 configured to transfer the carrier head 231 is generally coupled to the shaft 235. The swing arm 233 may transfer the carrier head 231 to a platen 237 for polishing a substrate or to adjacent the load cup 201 for transferring a substrate. The polishing station 230 may further comprise a motor 234 to rotate the carrier head 231 about a head central axis 213. A detailed description of the carrier head 231 may be found in U.S. Pat. No. 6,183,354, entitled “Carrier Head with a Flexible Membrane for a Chemical Mechanical Polishing”, and U.S. patent application Ser. No. 11/054,128 filed on February 8, now U.S. Pat. No. 7,001,257, entitled “Multi-chamber Carrier Head with a Flexible Membrane”, which are herein incorporated as reference.

The load cup 201 comprises a cup 202 having a recess 210 to retain a pedestal 203 configured to support and receive a substrate. The pedestal 203 is substantially circular and is supported by a shaft 205 extending from a pedestal central axis 211 through a hole 215 formed in the cup 202. The shaft 205 may be coupled to an actuator 214 which may be used to move the pedestal 203 vertically and to rotate pedestal 203. A detailed description of a similar pedestal may be found in U.S. patent application Ser. No. 10/988,647, now United States Patent Application Publication 2005/0176349, entitled “Load Cup for Chemical Mechanical Polishing”, which is incorporated herein as reference.

The cup 202 is supported by a shaft 206 extending from a pivoting axis 212. The shaft 206 is pivotably coupled to a support arm 207 which is configured to move the cup 202 horizontally, and/or vertically, and/or rotationally. A bearing 209 may be used between the shaft 206 and the support arm 207 to facilitate free pivoting between the shaft 206 and the support arm 207. In one embodiment, a releasable actuator 208 may be coupled to the shaft 206 to pivot the shaft 206 in a controlled manner. The shaft 206 may rotate freely when the releasable actuator 208 is in a released position and may rotate in a controlled manner when the actuator 208 is in a connected position. In one embodiment, the releasable actuator 208 may be a servo motor. In another embodiment, the releasable actuator 208 may be a spring.

The load cup 201 further comprises two alignment pins 204 protruding from the cup 202. The alignment pins 204 are positioned along a circle such that the distance between the alignment pins 204 to the pedestal center axis 211 equals an outer radius of the carrier head 231. The alignment pins 204 are configured to align the carrier head 231 with the load cup 201. The mechanism of this alignment will be discussed later. As shown in dashed lines, the head central axis 213 coincides with the pedestal central axis 211 when the carrier head 231 and the load cup 201 are aligned.

FIG. 3A illustrates a top view of the substrate transferring system 200 of FIG. 2. The load cup 201 is in a “home” position wherein the pedestal central axis 211 is in line with the support arm 207. FIG. 3B illustrates a top view of the substrate transferring system 200 at a pivoted position, wherein the pedestal central axis 211 is away from the support arm 207.

To align the carrier head 231 and the load cup 201, a relative motion may be performed to bring carrier head 231 and the load cup 201 adjacent. In one embodiment, the relative motion may be moving the load cup 201 horizontally towards the carrier head 231 by the support arm 207. In another embodiment, the relative motion may be rotating or translating the carrier head 231 towards the load cup 201. In another embodiment, the relative motion may be conducted by movement of both the carrier head 231 and the load cup 201.

FIG. 4A and 4B illustrate an exemplary method for aligning the load cup 201 and the carrier head 231. As shown in FIG. 4A, the load cup 201 is at the home position and the shaft 206 and the cup 202 are freely pivotable relative to the support arm 207. The head central axis 213 is not in line with the pivoting axis 212 and the pedestal central axis 211. The load cup 201 is pushed by the support arm 207 towards the carrier head 231. The pushing motion of the support arm 207 may continue until an outer surface of the carrier head 231 contacts one alignment pin 204 _(a). In one embodiment, a sensor may be used to sense the distance between the carrier head 231 and the load cup 201 and send signals for the load cup 201 to slow down prior to contacting the carrier head 231, therefore, reducing compact of contact.

Since the alignment pin 204 _(a) is in contact with the carrier head 231 and the cup 202 is freely pivotable relative to the support arm 207, the continuous pushing movement of the support arm 207 causes the cup 202 to glide and pivot about the pivoting axis 212 until the alignment pin 204 _(b) also in contact with the outer surface of the carrier head 231, as shown in FIG. 4B. The pushing movement of the support arm 207 may be stopped upon the contact of the alignment pin 204 _(b) and the carrier head 231. Because the distance from the alignment pins 204 to the central pedestal axis 211 equals the outer radius of the carrier head 231, the head central axis 213 coincides with the pedestal center axis 211 when the two alignment pins 204 _(a) and 204 _(b) are both in contact with the outer surface of the carrier head 231, hence, the carrier head 231 and the load cup 201 are aligned and ready for a substrate transferring.

In one embodiment, a sensor may be used on each of the alignment pins 204 _(a) and 204 _(b) to detect the contact between the alignment pins 204 _(a)/204 _(b) and the carrier head 231, hence determining an end point for the pushing movement of the support arm 207. In another embodiment, a threshold push force may be set for a driving mechanism connected to the support arm 207. When the support arm 207 encounters a resistant force greater than the threshold push force, the support arm 207 stops.

In one embodiment, the load cup 201 may be set to the same home position, for example, as the position shown in FIG. 3A, prior to every alignment process to achieve consistency of alignment. The releasable actuator 208 may be used to rotate the shaft 206 to set the home position and then release the shaft 206 for the cup 202 to rotate freely. In one embodiment, a sensor, such as an encoder or an optical flag, may be used to identify the home position.

The alignment apparatus and methods of the present invention is used to align a first and a second components, such as the carrier head 231 and the load cup 201. The first component, such as the load cup 201, comprises a pivoting joint, such as the joint of support arm 207 and the shaft 206, and two alignment pins, such as the two alignment pins 204. The pivoting joint allows the first component to freely rotate while the two alignment pins are finding the circumferences of the second component and guiding the first component to be concentric with the second component. The alignment apparatus and methods incorporate a contact mechanism of a surface, such as the circumference of the second component, to two points, such as the two alignment pins. Compared to the state of the art alignment mechanism, the present invention provides much simpler structure, yields more consistent alignment and much larger capturing range.

FIG. 5 schematically illustrates a partial top view of the substrate transferring system 200 of the present invention and illustrates a capturing range for the substrate transferring system 200. FIG. 5 show the relative position of the carrier head 231 to the load cup 201 prior to alignment. The pivoting axis 212 and the pedestal central axis 211 are positioned in a line 217 parallel to the support arm 207. The alignment pins 204 are positioned symmetrically on both side of the line 217. The distance between the pedestal central axis 211 and the pivoting axis 212 is A. The distance between from the alignment pin 204 to the line 217 is B. The distance from the head central axis 213 to the line 217 is C. When the alignment process is performed by a linear motion between the load cup 201 and the carrier head 231, and The linear motion is parallel to the line 217, the carrier head 231 may be captured by both alignment pins 204 as long as the distance C is not greater than the distance B, and the head central axis 213 may coincide the pedestal central axis 211 as long as the distance C is not greater than the distance A. To achieve proper alignment, the carrier head 231 must be captured by both alignment pins 204 and the head central axis 213 coincides the pedestal central axis 211. Therefore, the capturing range for this configuration is that the distance C is smaller than or equal to the smaller value of distance A and B. In one embodiment, for transferring 300 mm (12 inch) substrates, the distance A may be set to 3 inch, and the distance B greater than the distance A. Therefore, the capturing range is up to 6 inches.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

1. A load cup for transferring a substrate, comprising: a cup having a substrate supporting surface configured to support the substrate thereon; and two alignment pins protruding from the cup outside the substrate supporting surface, wherein the two alignment pins are both positioned at a first distance away from a center of the substrate supporting surface, and the cup is pivotable about a pivoting point positioned at a second distance away from the center.
 2. The load cup of claim 1, wherein the load cup is movable relative to a carrier head having a substrate receiving surface configured to receive the substrate, and the substrate may be transferred between the cup and the carrier head when the substrate receiving surface of the carrier head is aligned with the substrate supporting surface of the cup.
 3. The load cup of claim 2, wherein the two alignment pins are configured to be in contact with the carrier head so that when both of the two alignment pins are in contact with the carrier head, the substrate supporting surface of the cup is aligned with the substrate receiving surface of the carrier head.
 4. The load cup of claim 2, further comprising a sensing mechanism configured to stop the relative movement between the carrier head and the load cup.
 5. The load cup of claim 1, further comprising a motor adapted to rotate the cup about the pivoting point.
 6. The load cup of claim 1, further comprising a spring positioned around the pivoting point and adapted to bias the cup to a home position.
 7. A substrate transfer assembly, comprising: a load cup comprising: a substrate supporting surface having a center, the substrate supporting surface configured to support a substrate thereon; and two alignment pins protruding from the load cup at a first distance away from the center; a shaft extending from the load cup at a second distance away from the center; and a supporting arm pivotably connected to the shaft; and a carrier head having a substrate receiving surface configured to receive a substrate, the carrier head is relatively movable from the load cup.
 8. The substrate transfer assembly of claim 7, wherein the supporting arm is adapted to a moving mechanism configured to move the load cup relative to the carrier head.
 9. The substrate transfer assembly of claim 7, wherein the first distance is greater than an outer radius of the substrate supporting surface.
 10. The substrate transfer assembly of claim 7, further comprising a motor configured to pivot the load cup relative to the support arm.
 11. The substrate transfer assembly of claim 7, further comprising a spring configured to bias the load cup to a home position.
 12. The substrate transfer assembly of claim 7, further comprising a sensing mechanism to detect the position of the load cup relative to the carrier head.
 13. A method for aligning a load cup with a carrier head for transferring a substrate, comprising: providing two alignment pins extending from the load cup, wherein the two alignment pins are configured to align the load cup with the carrier head; providing a pivoting point about which the load cup may rotate, wherein the pivoting point is away from a central axis of the load cup; moving the carrier head and the load cup relatively such that the carrier head is in contact with one of the two alignment pins; pivoting the load cup about the pivoting point such that the carrier head is in contact with both of the two alignment pins.
 14. The method of claim 13, further comprising, prior to moving the carrier head and the load cup relatively, returning the load cup to a home position.
 15. The method of claim 14, wherein returning the load cup to the home position is performed by a motor configured to pivot the load cup about the pivoting point.
 16. The method of claim 13, wherein the distance from each of the two alignment pins to the central axis of the load cup equals an outer radius of the carrier head.
 17. The method of claim 13, wherein moving the carrier head and the load cup relatively comprises pushing the load cup towards the carrier head.
 18. The method of claim 13, further comprising providing a sensing mechanism to stop pushing the load cup after the carrier head is in contact with both of the two alignment pins.
 19. The method of claim 17, further comprising slowing down the load cup after the carrier head is in contact with one of the two alignment pins.
 20. The method of claim 13, wherein moving the carrier head and the load cup relatively comprises rotating the carrier head. 